1. Field of the Invention
This invention relates to a radiation image readout and reproducing apparatus for use in a radiation image recording and reproducing system, wherein read-out and reproduction of a radiation image are carried out by use of the same scanning system in the same apparatus.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to electric image signals, and the radiation image of the object is reproduced as a visible image by use of the image signals on a recording material such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store a radiation image until the sheet is scanned with stimulating rays to read out the radiation image. Therefore, after the radiation image is read out from the stimulable phosphor sheet, radiation energy remaining thereon should be erased for reusing the stimulable phosphor sheet.
In recent years, various attempts have been made to make small the aforesaid radiation image recording and reproducing system as a whole and to reduce the manufacture cost of the system. As one of such attempts, the applicant proposed in Japanese Patent Application No. 62(1987)-5263 a radiation image read-out and reproducing apparatus wherein read-out and reproduction of an image stored on a stimulable phosphor sheet are carried out by use of the same subscanning system in the same apparatus, and wherein the apparatus as a whole is made small and the manufacture cost thereof is reduced by integrally combining a read-out apparatus with a reproducing apparatus which have heretofore been provided independently.
In the case where the read-out apparatus and the reproducing apparatus are combined integrally such that a single sub-scanning means is used for both the image read-out and the image reproduction, the generation of the image signals by the read-out from the stimulable phosphor sheet and the reproduction of the radiation image of an object by use of the image signals can be carried out with a single apparatus. On the other hand, the conventional system for obtaining an X-ray image of an object by use of an X-ray film is still used frequently. Also, even though the conventional system using the X-ray film is replaced by the radiation image recording and reproducing system using the stimulable phosphor sheet, a large number of the X-ray films on which an X-ray image was recorded in the past have heretofore been stored and should still be processed. Furthermore, diagnostic apparatuses such as a CT and a US are often used in recent years, and a large number of films on which an image generated by these diagnostic apparatuses is recorded should be processed. Therefore, it is desired that the image recorded on each of these films be read out photoelectrically, and the image signals thus obtained be image-processed in the same manner as the image signals detected from the stimulable phosphor sheet, stored and used for the image reproduction.
For the aforesaid purposes, it has heretofore been necessary to use a film read-out apparatus for photoelectrically detecting the image recorded on the film independent of the radiation image recording and reproducing system using the stimulable phosphor sheet. Therefore, even though only the radiation image recording and reproducing system using the stimulable phosphor sheet is improved and made small, the overall system including the function of the image read-out from the film could not be made so small and the manufacture cost thereof could not be reduced so much.